Mathematical Model Predicts Low Probability of Intelligent Life Elsewhere in Universe

May 5, 2008

A mathematical model produced by Andrew Watson (University of East Anglia) suggests that the probability of intelligent life on any Earth-like planet is just about zero.

According to Watson, “The Earth’s biosphere is now in its old age and this has implications for our understanding of the likelihood of complex life and intelligence arising on any given planet." Watson predicates his hypothesis on solar models that imply the brightness of Earth's sun is increasing, and temperature models that suggest that the remaining life span of Earth is "only" about a billion years--a short time span when compared to the four billion years since life first appeared on Earth. Therefore, habitability on any Earth-like planet would, according to Watson, follow the same pattern.

Applying the idea of limited lifespan idea to a stepwise model, Watson posited that four major evolutionary steps would have occur before an intelligent civilization could come into existence: the emergence of single-celled bacteria; complex cells; specialized cells allowing complex life forms; and intelligent life having a comprehensive language.

His model, published in the journal Astrobiology, proposes that the upper limit for the probability of each step is 1/10. Each discrete step is independent of any other and can only take place after previous steps in the sequence. They would be evenly spaced throughout a planet's history, which would be consistent with the major transitions that have been identified in the evolution of life on Earth.

Single-celled life would emerge about half a billion years after a planet's formation; multi-cellular life would come about a billion and a half years later; specialized cells allowing complex life forms with functional organs would come into being a billion years afterwards; and language a billion years later.

According to the model, the chances of intelligent life emerging elsewhere over four billion years are less than 1/10,000. Watson concluded that "Only on those rare planets on which complex creatures happen to evolve can there exist observers who ask questions about evolution and care about the answers.”

Source: University of East Anglia News